Numerical study on the effect of loading on the admittance signatures acquired in the electromechanical impedance technique

• Main Author: Lim, Darren Tze Yang.
• Other Authors: Soh Chee Kiong
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Civil engineering::Structures and design
• Online Access: http://hdl.handle.net/10356/40214
• Institution: Nanyang Technological University

Structural health monitoring (SHM) forms an integral part in maintaining the reliability and serviceability of the structures in every one’s everyday life. The application of electromechanical impedance (EMI) technique in SHM provides an indication for damage detection by reflecting changes in the stiffness of the structure. Simulation using finite element method (FEM) to apply EMI techniques helps analyst in understanding the behaviour of the structure materials and allow the analyst to determine the state of health of the structures. This report discusses the influence that the damping value of a piezoceramic transducer (PZT) has on the recorded conductance signature via simulation through FEM. The study will concentrate on the effects of the damping value on a free-hanging PZT patch and a simple aluminium beam with a PZT transducer bonded at the centre. Comparison will be made between numerical and experimental results whereby the damping value of the PZT transducer will be adjusted to match both sets of results. A structural component subjected to an external load will be simulated by a simple beam under the effects of axial load. Through simulation and comparison with previous studies, the feasibility of using FEM to simulate static loading on the structure and the effects of the loading on the admittance signatures will be discussed. An increase in the damping of the PZT patch will lead to a reduction in the rate of reaction in the material hence resulting in a decrease in the conductance signature acquired. However for a simple beam bonded with a PZT patch, the effects of the damping value in host structure material will play a more important role in influencing the conductance signature than that of the PZT patch. A rightward shift of the modal frequency of a simple beam simulation would occur under the effects of a tensile load larger than 50 kN acting on the beam. The observation from this study coincides with the observations from previous studies showing the feasibility of using FEM in the application of EMI technique simulating static loads on the structure. This study also reinforced the theory that the damping value of the PZT patch has a degree of influence in the conductance signature acquired, though the damping property of the host structure will have a bigger influence in a beam-PZT patch combination. Further studies on the actual degree of influence of the damping property in the host structure and other material property such as electric permittivity matrix can be carried out. The effect of static loadings acting on the admittance signature acquired can also be further studied for the other frequency ranges above 100 kHz.